The question ‘what is law?’ is one of the most fundamental in legal philosophy, yet it has no single, universally accepted answer. Jurisprudence, the theory of law, offers various perspectives on the nature, sources, and function of law. This essay will briefly examine three prominent theories that provide different answers to this question: natural law, legal positivism, and legal realism. By exploring these distinct schools of thought, it becomes clear that the definition of law is dependent on the theoretical lens through which it is viewed.
Natural Law Theory
Natural law theory is one of the oldest theories of law, proposing that there is a necessary connection between law and morality. According to this view, there exists a 'higher law', derived from sources such as God, reason, or nature, which all human-made (or 'positive') laws must follow to be considered truly valid. A key tenet of this theory is captured in the maxim lex iniusta non est lex, meaning an unjust law is not a true law (Wacks, 2020). Thinkers like St Thomas Aquinas argued that positive law derives its validity from natural law, and any law that contradicts the principles of natural justice is a 'perversion of law'. More modern proponents like John Finnis have developed secular versions, identifying a set of basic human goods that law should serve to protect and promote. Therefore, for a natural lawyer, defining law involves not just looking at what rules have been formally enacted, but also evaluating their moral content. A law that is grossly unjust, such as one mandating genocide, would be considered legally invalid from a natural law perspective, regardless of whether it was passed by a legitimate government.
Legal Positivism
In direct contrast to natural law, legal positivism insists on the separation of law and morality. For positivists, the validity of a law depends not on its moral content but on its source. If a law has been created through the recognised procedures of a given society, it is a valid law. This is often referred to as the 'separation thesis' (Hart, 2012). The early positivist John Austin defined law simply as the command of a sovereign, backed by the threat of a sanction. A more sophisticated version was developed by H.L.A. Hart, who described law as a system of rules. Hart (2012) argued that a legal system consists of 'primary rules' (which impose duties, such as the criminal law) and 'secondary rules' (which confer powers, such as rules for making contracts or statutes). The validity of these rules is determined by a fundamental 'rule of recognition', which is a social convention accepted by officials for identifying law. From a positivist viewpoint, a law can be legally valid even if it is morally repugnant. The question of whether one ought to disobey an unjust law is a separate moral question, but it does not change the law's legal status.
Legal Realism
Legal realism offers a different approach, moving away from abstract definitions to focus on the practical realities of the legal system. Arising primarily in the United States in the early 20th century, realism is sceptical of the idea that law is simply a body of rules found in books. Instead, realists argue that the law is what judges and other officials actually do. As Oliver Wendell Holmes Jr. famously stated, "The prophecies of what the courts will do in fact, and nothing more pretentious, are what I mean by the law" (Holmes, 1897). Realists emphasise that the formal rules are often vague or incomplete, and that judges' decisions are influenced by their personal beliefs, political views, and other non-legal factors. This perspective sees a gap between the 'law in the books' and the 'law in action'. For a legal realist, to understand what the law is, one must observe the behaviour of the judiciary and predict its decisions, rather than just analysing statutes and case precedents.
Conclusion
In conclusion, the question 'what is law?' elicits different responses from the three theories examined. Natural law defines law by reference to a higher moral standard, asserting that its validity is tied to justice. Legal positivism, by contrast, defines law as a set of rules created by a recognised social or political authority, separating its legal validity from its moral worth. Finally, legal realism shifts the focus from rules to practice, defining law as the actual behaviour and decisions of legal officials, particularly judges. These theories demonstrate that there is no simple definition of law; instead, each provides a valuable but distinct framework for understanding its complex nature, whether as a moral command, a social fact, or a practical reality.
References
- Hart, H.L.A. (2012) The Concept of Law. 3rd edn. Oxford: Oxford University Press.
- Holmes, O.W. Jr. (1897) 'The Path of the Law'. Harvard Law Review, 10(8), pp. 457-478.
- Wacks, R. (2020) Understanding Jurisprudence: An Introduction to Legal Theory. 6th edn. Oxford: Oxford University Press.

